1. Field of the Invention
The invention concerns a magnetic bearing for active magnetic centering and, particularly, a magnetic bearing of modular construction having a removably attached ferromagnetic core and coil.
2. Description of the Prior Art
Examples of magnetic bearings are described in European Patent 0 284 487 and U.S. Pat. No. 4,470,644.
The aforementioned bearings essentially differ from one another in that, in U.S. Pat. No. 4,470,644, the permanently magnetized members are carried by a body separate from that on which the coils are mounted whereas in European Patent 0 284 487 the permanently magnetized members are mounted on the same body as the coils.
In practice the coils of the magnetic bearings of the aforementioned type are fitted onto cores disposed between two ferromagnetic plates, the flux lines passing longitudinally through the cores, entering and leaving the cores at their edges. Accordingly, access to these cores is possible only during manufacture (access is impossible once assembly of the bearing is completed and necessarily so once the bearing is mounted in a system ready to operate). Moreover, good control of the field requires excellent control of the height of the cores so that their edges are exactly where required, against the ferromagnetic plates (or against one of these plates and against a static shim forming an airgap, as recommended in the aforementioned European Patent 0 284 487). This control can be difficult if more than one core has to be positioned between the same two plates.